A variety of metal scaffolds are known. The present invention relates specifically to modular scaffold systems whose principal components are vertical uprights carrying horizontal flanges and transverse braces carrying connectors that cooperate with the flanges. Each flange will typically have a set of openings in a predetermined spacing arrangement that permit braces to be receive at different angles. Each connector will typically have upper and lower sections defining a mouth that receives a flange and aligned openings that register with one of the flange openings. A wedge is inserted through the registered openings to secure the joint between the brace and the upright. In some systems, the wedge may force leading surfaces of the connector into a friction lock with the upright. The friction lock is intended to reduce shear and bending forces that might otherwise be applied to the flange through the brace. Several similar flanges are welded at intervals to the upright to permit fastening of braces at various locations.
Such scaffolds have been constructed of steel. Examples of such scaffolds are to be found in U.S. Pat. No. 4,044,523 to Layher, U.S. Pat. No. 4,493,578 to D'Alessio, and U.S. Pat. No. 4,840,513 to Hackett. To the knowledge of the present inventor, no aluminum scaffold system of similar overall configuration has been successfully commercialized.
The present specification proposes a scaffold with a predominantly aluminum construction. One immediate and readily expected advantage is a reduction in the weight of the braces and uprights. However, aluminum poses unique problems. In particular, welding an aluminum flange to a tubular aluminum post can significantly weaken the post. The Canadian Standards Association typically ascribes a 40% reduction in load-bearing capacity once any significant weld is formed on such posts. Multiple flanges should, of course, be vertically registered (specifically their vertical openings). Irregularities may otherwise prevent braces from properly meeting with flanges when braces are joined between pairs of uprights. One problem in that regard is that aluminum is not a "forgiving" material. Any re-working of the position of a flange, particularly additional welding, is apt to significantly weaken the associated post. The weakness of aluminum relative to steel also creates the risk of snapping flanges in response to loads applied through braces connected to a flange. Loose fits between brace connectors and flanges may cause wear in relatively soft aluminum materials. Simply increasing overall dimensions and the quantity of aluminum in scaffold components is not a truly viable solution, as the resulting system is apt to be at a significant cost disadvantage relative to conventional steel systems. Various aspects of the present invention address such problems.